Shop Tips » Stitch & Glue Boatbuilding Tips
Most stitch-and-glue boats should be built from marine grade mahogany plywood. There are several types of mahogany plywood that may be used, but okoume, a plantation grown African mahogany, is the most economical and the most common. Other species, such as khaya and sapele are also suitable, if a little heavier.
When buying mahogany plywood, look for a stamp reading BS1088, or British Standard 1088. This is the minimum grade acceptable for boat building. You may also find plywood that's made to Lloyds specifications; such plywood also meets BS1088. We've recently seen okoume plywood that's stamped BS6566. This is an exterior grade plywood that often has very thin face veneers and may contain voids. It is not suitable for building hulls, but it can be used for some decks and interior components.
Larger boats that require 2-inch or thicker plywood may be built from fir marine plywood. Fir is heavier than okoume and doesn't look good varnished, but it is less expensive. Fir is also much harder to finish because it almost always checks, or develops minor surface cracks, unless covered with glass cloth.
A few builders have built stitch-and-glue boats from lauan or fir exterior grade wood. Unless the boat being built is specifically designed to be built from exterior grade plywood, this is a foolish and potentially dangerous practice. Exterior grade panels often contain voids that can cause the panel to suddenly crack. In addition, the exterior veneers, which are most important for strength, are often very thin. Exterior grade panels also take more time to finish than the better marine grades, so you'll lose in time what you'll have saved in cost. Finally, consider that even with marine grade plywood, the plywood panels are less than one third the cost of the materials used in most boats. If a panel fails you'll have wasted not only the plywood, but also expensive fiberglass, epoxy, and other materials.
There is relatively little solid wood used in stitch-and-glue boats. Most of the parts such as sheer clamps, carlins, deckbeams, or seat risers can be made from any strong but light wood that takes glue well. Fir, cypress, spruce, mahogany or Atlantic white cedar (not red cedar) are all good choices. Decorative parts such as rubrails, trim strips, and coamings can be made from dark mahogany, cherry, Spanish cedar, or teak. If a boat has a sapele or khaya deck, light trim looks nice; ash or white oak would be good choices. If you're a cabinet maker you may have a stash of suitable hardwood, but be sure that the species you use is a "boat building wood;" some woods such as poplar and birch tend to discolor or rot quickly in a marine environment.